Rakudo Perl 6 and Parrot Jonathan Worthington Linuxwochenende 2008
Rakudo Perl 6 and Parrot Me � From England
Rakudo Perl 6 and Parrot Me � From England � And yes, I do like tea…
Rakudo Perl 6 and Parrot Me � From England � And yes, I do like tea… � …but I prefer it without milk in.
Rakudo Perl 6 and Parrot Me � From England � And yes, I do like tea… � …but I prefer it without milk in. � Currently living in Bratislava, Slovakia.
Rakudo Perl 6 and Parrot Me � From England � And yes, I do like tea… � …but I prefer it without milk in. � Currently living in Bratislava, Slovakia � Just an hour from here � Like Vienna, it's beautiful…
Rakudo Perl 6 and Parrot Me � From England � And yes, I do like tea… � …but I prefer it without milk in. � Currently living in Bratislava, Slovakia � Just an hour from here � Like Vienna, it's beautiful… � …but beer only costs 1 euro a pint �
Rakudo Perl 6 and Parrot Me � From England � And yes, I do like tea… � …but I prefer it without milk in. � Currently living in Bratislava, Slovakia � Just an hour from here � Like Vienna, it's beautiful… � …but beer only costs 1 euro a pint � � Er, half litre
Rakudo Perl 6 and Parrot My Talk � An overview of three technologies � The Parrot VM – a virtual machine for dynamic languages � The Parrot Compiler Toolkit (= PCT) – a tool chain for rapidly developing compilers targeting Parrot � Rakudo, a Perl 6 implementation on Parrot built using PCT
Rakudo Perl 6 and Parrot Parrot
Rakudo Perl 6 and Parrot Parrot Is A Virtual Machine � Virtual instruction set � Hides away the details of the underlying hardware � Interface to IO, threading, etc. � Hides away the details of the underlying operating system � "Write once, run anywhere" � Or as close as is realistically possible
Rakudo Perl 6 and Parrot Register Architecture � .Net CLR and JVM are stack based � Parrot is register based � Faster to interpret, since no stack pointer to keep (need to run on many odd platforms; shouldn't rely on JIT) � A little easier to JIT-compile too; "just" a register allocation problem � Variable sized register frames per sub
Rakudo Perl 6 and Parrot HLL Feature Support � Parrot provides support for a range of high-level language features � By providing support for them at the VM level… � Compilers for different languages don't need to re-invent the wheel � Different languages can inter-operate
Rakudo Perl 6 and Parrot Examples Of HLL Features In The VM � Common set of calling conventions � Multiple dispatch � Classes, attributes, methods, objects, inheritance, introspection (reflection) � Namespaces � Continuations, co-routines, closures � Lexically scoped variables � And more…
Rakudo Perl 6 and Parrot But Languages Are Different! � We want to support a load of existing languages � Python � Ruby � PHP � JavaScript � But they all have slightly different ideas about how certain things work…
Rakudo Perl 6 and Parrot PMCs � PMC = Parrot Magic Class � Implement some of a fixed set of methods that perform a range of common operations � Range from simple things, like get an integer representation of this thing… � …to more complex OO-related things, such as adding a parent class
Rakudo Perl 6 and Parrot Examples Of PMCs � Integer PMC – implements methods relating to arithmetic � Array PMC – implements methods relating to keyed access � Class PMC – implements object orientation related methods � Sub PMC – implements invoke method, and a few others (name, etc.)
Rakudo Perl 6 and Parrot Different Semantics, Common Interface � The PMCs all provide the same interface � Languages can implement this common interface to provide their own semantics � For example, a Perl array can return "undefined" on access to an out-of- range element, whereas a Java array could throw an exception
Rakudo Perl 6 and Parrot Extensibility � Don't need to have all the PMCs in the Parrot core; can build them into a dynamically linked library � Can also dynamically load additional opcodes (instructions), to augment the VM's instruction set � Language distribution = compiler + (optionally) PMC Library + (optionally) Opcode Library
Rakudo Perl 6 and Parrot PIR � Parrot Intermediate Representation � Essentially, the Parrot VM's "assembly" � However, for some common things (like method calls), it turns some syntactic sugar into the several real instructions it takes to do it � Also does register allocation for you, so compiler writers needn't worry about it
Rakudo Perl 6 and Parrot Some Simple PIR Examples � "Hello, world!" – of course .sub 'main' :main print "Hello, world!\n" .end � Compute The Answer .sub 'main' :main $I0 = 25 $I1 = 17 $I2 = $I0 + $I1 print $I2 print "\n" .end
Rakudo Perl 6 and Parrot Some Simple PIR Examples � Factorial .sub 'fact' .param int n if n > 1 goto rec .return (1) rec: $I0 = n – 1 $I1 = fact($I0) $I1 *= n .return ($I1) .end
Rakudo Perl 6 and Parrot Parrot Compiler Toolkit
Rakudo Perl 6 and Parrot Writing Compilers Is Easy… � …if you have the right tools � PCT aims to be a Right Tool � You write the "front end": � Grammar, which specifies syntax � Actions, to produce an Abstract Syntax Tree from the Parse Tree � The backend (from the AST down to Parrot bytecode) is done for you
Rakudo Perl 6 and Parrot Compilation Process Program Source Parse Tree Abstract Syntax Tree Opcode Syntax Tree PIR (Parrot IL) Parrot Bytecode
Rakudo Perl 6 and Parrot Compilation Process Program Source PGE Parse Tree NQP Abstract Syntax Tree PCT Opcode Syntax Tree PCT PIR (Parrot IL) Parrot Parrot Bytecode
Rakudo Perl 6 and Parrot Compilation Process Program Source PGE Parse Tree NQP Abstract Syntax Tree PCT Opcode Syntax Tree PCT PIR (Parrot IL) Parrot Parrot Bytecode
Rakudo Perl 6 and Parrot Compilation Process Program Source PGE Parse Tree NQP Abstract Syntax Tree PCT Opcode Syntax Tree PCT PIR (Parrot IL) Parrot Parrot Bytecode
Rakudo Perl 6 and Parrot PGE = Parrot Grammar Engine � Implementation of Perl 6 rules � A bit like regexes, but taken a step further so we can use them to write a full grammar � Unlike more traditional tools like lex and yacc, where you write a tokenizer and a grammar, here you just write the parse rules and the tokenizer is generated for you
Rakudo Perl 6 and Parrot An Example Rule � You use PGE to write the grammar for your language � For example, here's how we could parse an if statement rule if_statement { 'if' <expression> <block> {*} } � You put a {*} in place to indicate that we should run an action
Rakudo Perl 6 and Parrot Compilation Process Program Source PGE Parse Tree NQP Abstract Syntax Tree PCT Opcode Syntax Tree PCT PIR (Parrot IL) Parrot Parrot Bytecode
Rakudo Perl 6 and Parrot NQP = Not Quite Perl 6 � A subset of Perl 6 � Contains just enough to allow you to produce an Abstract Syntax Tree from the parse tree � Variables and literals � Binding (but not assignment) � Conditionals and loops � Object instantiation and method calls
Rakudo Perl 6 and Parrot NQP = Not Quite Perl 6 � This method is called when the parser encounters the {*} in the grammar method if_statement($/) { my $then := $( $<block> ); $then.blocktype('immediate'); my $past := PAST::Op.new( $( $<EXPR> ), $then, :pasttype('if'), :node( $/ ) ); make $past; }
Rakudo Perl 6 and Parrot NQP = Not Quite Perl 6 � We are passed $/, the match object, which describes what was parsed method if_statement($/) { my $then := $( $<block> ); $then.blocktype('immediate'); my $past := PAST::Op.new( $( $<EXPR> ), $then, :pasttype('if'), :node( $/ ) ); make $past; }
Rakudo Perl 6 and Parrot NQP = Not Quite Perl 6 � Named captures ($<….>) give you the match object for the sub rules method if_statement($/) { my $then := $( $<block> ); $then.blocktype('immediate'); my $past := PAST::Op.new( $( $<EXPR> ), $then, :pasttype('if'), :node( $/ ) ); make $past; }
Rakudo Perl 6 and Parrot NQP = Not Quite Perl 6 � Writing $( $<…> ) gets you the AST for that match object method if_statement($/) { my $then := $( $<block> ); $then.blocktype('immediate'); my $past := PAST::Op.new( $( $<EXPR> ), $then, :pasttype('if'), :node( $/ ) ); make $past; }
Rakudo Perl 6 and Parrot NQP = Not Quite Perl 6 � We instantiate a new AST node of type Op method if_statement($/) { my $then := $( $<block> ); $then.blocktype('immediate'); my $past := PAST::Op.new( $( $<EXPR> ), $then, :pasttype('if'), :node( $/ ) ); make $past; }
Rakudo Perl 6 and Parrot NQP = Not Quite Perl 6 � This node has two children: the condition and the block to run method if_statement($/) { my $then := $( $<block> ); $then.blocktype('immediate'); my $past := PAST::Op.new( $( $<EXPR> ), $then, :pasttype('if'), :node( $/ ) ); make $past; }
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